Something from the officer that most likely first picked up the wrapper on the 6th floor. Doesn’t seem to be in the “Studebaker position" after all does it?
So the wrapper was not originally picked up by Montgomery in the "Studebaker position". It would explain why so many officers who observed the SN prior to the discovery of the rifle failed to mention it. It wasn't there! Likely it was placed in the corner at a later time.
Logical assumption?